Day 1 Severe Weather Outlook

Valid 071300Z – 081200Z


Isolated severe thunderstorms are possible for another couple hours
in the eastern Virginia/central Maryland area.

In mid/upper levels, broadly cyclonic flow will continue to cover
most of the CONUS east of the Rockies, as a major synoptic-scale
trough progresses eastward from the Mississippi Valley and upper
Great Lakes. A basal shortwave trough — located initially over the
southern Appalachians — is forecast to eject northeastward across
most of New England by 00Z, with a trailing vorticity lobe
southwestward to the eastern Carolinas. A weaker/upstream
perturbation — now over the northern Rockies — will amplify
somewhat at it moves southeastward toward the mean trough position.
By the end of the period, this shortwave trough should reach the
Mid-South region. Farther upstream, a strong shortwave trough was
evident in moisture-channel imagery over the northeastern Pacific
near 138-140W, west of the Pacific Northwest. This perturbation
will move inland across BC and the Northwest during the 06-12Z time

At the surface, 11Z analysis showed a low over the extreme northern
VA/northwestern MD area, with occluded front southeastward to the
northern Outer Banks of NC. A cold front extended from there
offshore from the rest of NC, SC and GA, and across south FL. A
secondary cold front was drawn from the low southwestward across
western NC to central AL. The low should deepen further and eject
northeastward across the Mid-Atlantic and southern/eastern New
England through 00Z. The leading cold front will sweep well
offshore of the Atlantic Coast through the period, with the
secondary front catching up and/or blending into the background
environment of cold advection following the first.

Widely scattered showers and isolated thunderstorms should move
rapidly northeastward across portions of VA/MD through the remainder
of the morning, along and ahead of the secondary front. Very
isolated/brief gusts to near severe limits or a brief tornado cannot
be ruled out in a regime of strong deep-layer forcing for ascent,
strong flow in low/middle levels, and steep low-level lapse rates,
but marginal/shallow buoyant layer. See SPC mesoscale discussion
105 for near-term details. This regime may spread into parts of
southeastern PA and southern NJ before outrunning favorable

..Edwards.. 02/07/2020


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